Phase correcting arrangement for electronic type selecting systems



Dec. 30, 1947. H; A. BURGESS PHASE CORRECTING ARRANGEMENT FOR. ELECTRONIC TYPE SELECTING SYSTEMS Filed July 6, 1945 5 Sheets-Sheet l I I'H /A/l ENT HA BURGESS A TTORNEV Dec. 30, 1947. 'H. A. BURGESS PHASE CORRECTING ARRANGEMENT FOR ELECTRONIC TYPE SELECTING SYSTEMS Filed July 6, 1945 5 Sheets-Sheet 2 FIG? SHG

s E %w :1: WA H W m ||1|L w 0 5 4 VI 4 G. w EL L IILP w 7 5 4 till; I; I A w N ATTORNEY Dec. 30, 1947. H. A. BURGESS PHASE CORRECTING ARRANGEMENT FOR ELECTRONIC TYPE SELECTING SYSTEMS Filed July 6, 1945 5 Sheets-Sheet 5 Dec. 30, 1947. H. A. BURGESS PHASE CORRECTING ARRANGEMENT FOR ELECTRONIC TYPE SELECTING SYSTEMS Filed July 6, 1945 5 Sheets-Sheet 4 FIG. 5

lNl/EN 70/? H. ,4. BURGESS ATTORNEY Dec. 30, 1947. H.'A. BURGESS PHAS E CORRECTING ARRANGEMENT FOR ELECTRONIC TYPE SELECTING SYSTEMS Filed Jul 6, 1945 5 Sheets-Sheet 5 //v l/EN TOR H. A. BURGESS ATTORNEY Patented Dec. 30, 1947 UNITED STATES PATENT cFFlcE PHASE CORRECTING ARRANGEMENT. FOR ELECTRONIC TYPE SELECTING SYSTEMS Harry A. Burgess, Ghathani', N. 3., as's ighor to Bell Telephone Laboratories; Incorporated, :New York,'N. Y., a corporation of New York Application July 6, 1945; sate: No; "60237 1 12 Claims.

Thisinvention relatesto high speed telegraphy. It is an object of theinvention to provide a high speed telegraph system in which the signals m y be transmitted over long distances and the corresponding characters recorded by means of apparatus using a minimum of mechanical operations. V

It is a further object of the invention to provide a sy'stem of this type as well as a method of high s eed recording ofsignals, in which advantage is taken of the high'operating speeds and accurate 'performanceat such fhigh speeds of electronic and optical ormagnetic devices.

It is a further object to provide ,a system of this type in which the me'ssage may be originally I set up in the usual manner of commercial telegraph messages and with the sa me speed, but in which the messages are transmitted at very high speeds limited only by the operating speeds of electronic and optical devices.

It is a still further object to provide a signal- I ing system in which the high speed of signaling and the nature of the signa s will secure adegree of secrecy of the message while it passes over the transmission channel;

It is a more specific object of the invention to provide an electronic type receiving system for high speed signals which will operate accurately under practical conditions where variations and discrepancies in transmission maybe expected.

"In accordance-with a feature of the invention the signals from a high speed channel are received by an electronic discharge device, such as a cathode ray tube, in which the projected beam of electrons normally sweeps in a predetermined :track in synchronism and phase with the incoming signals and in which t'he'beam or ray is deflected once for each circular sweep by the incoming signals for the purpose of selection.

In accordance with another feature of the invention the signals of the letters of the alphabet or other signs or characters are represented in the high speed channel by an impulse with a definite phasing 'or space relation from the initial time instant ofeach letter or character cycle, so

that upon arrival at the receiving cathode ray tube the beam will be deflected after having traveledan angular distance around its predetermined path corresponding to the phasing or position of the received impulsewithin its cycle. 7

The deflected beam thus is enabled to select a character for recording corresponding to the transmitted character.

7 Inaccordance with ,a more specific feature of the invention the (J&th0de ray tube is provided with a circular plate or {screen placed in the circular path bf the beam to normally prevent the beam from passing bydnd this screen. The plate has a series of differentiated areas arranged in a circle concentric with the normal circular path of the beam but of a different diameter. These target areas have perforations or stencil cut-outs differently shaped to form letters or signs or other characters an-dthe cut-cut portions permit the beam to pass beyondthe plate. Whereas in the preferred form the beam is initially produced with a shape to form a small circular spot upon the plate, the beam will be shaped in passing through the stencils to throw an imageor shadow on a fluorescent screen-at the end ofthe tube wh ch will have an outline corresponding to the contours of the perforation-s in thescreen, The letters or characters may be read on the fluorescent screen on a circle'along itsperiphery or may be optically recorded at high speed. i H In accordance with a still more specific feature of the invention thebeam after passing through the cutouts-is deflected to continually strike in a centralspot on the fluorescent screen so that all successvie chara'cters-will'be readable at this spot "for recording.

- a predeterminedlength.

In accordance-with a principal feature of the invention auxiliary electrodes are provided near the target areas which are connected through suitable phase shifting equipments to the sweep producing electrodes so that the sweep of the "beam may be accelerated" or retarded whenever the beam strikes cheer the auxiliary electrodes.

The invention will new be described more detail as applied to a commercial transmission system including several distinct features; it should, however, be understood that the invention is not limited to the-particular embodiment disclosed hereinafter, and that its scope is defined-by the appended claims.

is the following detailed -desc'ription' reference will be made to the accompanying drawings showing schematically the essential elements of a complete telegraph system embodying the features of the invention and in which:

Fig. 1 shows diagrammatically a transcription equipment for producing the original message in recorded form for retransmission over a high speed channel;

Fig. 2 shows a schematic circuit arrangement for transmission of the recorded message at high speed over a radio channel;

Fig. 3 shows a schematic circuit arrangement for receiving the high speed signals and shows a diagrammatic view of a cathode ray tube partly in perspective and including various control elements;

Fig. 3A shows a suitable camera for recording the message at high speed;

Fig. 4 shows a sample portion of the recorded message used at the transmitting station;

Fig. 5 is a cross-sectional view taken on line 55 in Fig, 3 through the cathode ray tube, and includes the printing record;

Fig. 6 is a detailed view of the stenciled screen or target used in the cathode ray tube for producing the letters of the alphabet or other desired characters. This figure also includes a simplified showing of equipment for lining up the system at starting and for maintaining synchronism during operation; and

Fig, '7 shows more in detail the circuits of the starting and synchronizing equipment indicated in Fig. 6.

Referring now more particularly to the diagram shown in Fig. 1 the initial recording system shown in this figure is adapted for control by a perforated message tape, generally of the type used in commercial telegraph practice, for the production of a magnetic or optical record on a wire or tape better adapted than a perforated tape for high speed transmission of the message.

The system shown in Fig. 1 includes a tape transmitter T, a set of permutation relays P, a set of storing relays S, a continuously rotating distributor D and a recording light valve V.

trary function signals such as shift and unshift,

space, line feed, etc. In such case, it would, of course, be necessary to use a six or seven-unit code for producing the perforated tape with the original message, or to use the five-unit code with some case shift arrangement.

It should furthermore be understood that in case the original message may be recorded at comparatively slow speed in the form it is needed for the high speed transmission, it is not necessary to first produce a perforated record tape, but the keyboard may be provided with permutation bars and transmitting contacts which will be locked upon operation by the keys and will be unlocked automatically by the system for resetting. Such a keyboard would replace the transmitter T in Fig. 1. In this case, the speed must be low enough to permit the operator to operate in unison with the automatic unlock- 4 ing operation. A transmitting device of this kind is shown in Fig. 1'79 in a book by H. H. Harrison entitled Printing Telegraph Systems and Mechanisms and issued by Longmans, Green and Company, New York, in 1923.

If the permutation bars be omitted from the keyboard and each key provided with sending contacts the keyboard would replace both the transmitter T and the permutation relays P shown in Fig. 1 and its contacts would be connected directly to .the storing relays S.

The objects of the circuit shown in Fig. 1 may be attained in a variety of other well-known ways. However, since this part of the system does not include any feature of the invention it is not believed necessary to further describe such alternative forms or to illustrate in the drawing those referred to above.

by a driving means 65.

The circuit shown in Fig. 1 has the advantage of being adapted for operation at speeds approaching the speed of transmission in the taletypewriter plant.

For the purpose of operating the system shown in Fig. 1, the perforated tape may be prepared by a tape puncher such as that shown in Fig. 166 in the book by Harrison referred to above. The prepared tape is inserted in the transmitting device T which may be of the type generally known as an automatic transmitter which is extensively used, for example, in the multiplex telegraph system. A transmitter of this type is shown in Fig. 179 in the book by Harrison referreed to above. The transmitter includes five sending contacts I, 2, 3, 4, 5 and a resetting magnet ID for advancing the tape from character to character. For a code of six or seven units, the transmitter should of course, be provided with six or seven sending contacts.

As shown in Fig. 1, the sending contacts are connected to a set of permutation relays P with contacts for operating any selected one of the storing relays S. The storing relays are adapted to be self-locking and to ground a segment on the distributor D for control of the recording device V. There is one storing relay for each character in the alphabet used in the system.

Th distributor D has a number of circular contact tracks and a contact arm which is motordriven at constant speed in any suitable manner The distributor has a series of short segments 5| each connected to the grounding contact of a storing relay and cooperating with an annular contact ring 52; a contact brush 58 on the distributor arm 51 connects the ring 52 to the segments 5| in succession. The segments 5| are distributed over the complete circle of the distributor, except over an angular portion of a width equal to the width of a few of the segments 5|, say about six segments. Each segment 5| is about half the width of the center spacing between the segments. A pair of control rings 55 and 56 are interconnected by means of the brush 59 on arm 51. The ring 55 is interrupted in the angular space from which the segments 5| are omitted, as just described.

The distributor shaft BI is directly connected or geared to a driving sprocket 62 in the recording device V. The driving sprocket 52 is for feeding a recording strip 60, such as a photographic film, with a continuous speed before an optical recording devic 10. The device Iii is of the type known as a light valve in Which an electrically operated shutter arrangement 1| controls a light beam from a light source 12 in response to incoming impulses. The light beam is projected through the shutter 1| and is projected by a suitable lens system 3 upon the photographic film 60. The light recording system is properly enclosed in a light-proof enclosure 15.

- The recording equipment shown in Fig. 1 may be briefly described as operating as follows:

It will be assumed that the storing relay 34 has already been operated and, therefore, is locked up over a circuit from battery through its lefthand make contact, left winding, conductor 40 and over distributor rings 55 and 56 to ground; relay 34 at its right-hand make contacts applies ground to segment for recording of a character on the film 60. u

The stepping relay 2!] is also locked over the rings 55 and 56 to ground.

Th transmitter T will be assumed to have received a new setting from the punches in the perforated tape in accordance with which contacts 3 and 5 are closed. Accordingly, battery is applied over contacts 3 and 5 to the windings of permutation relays l3 and I5; the remaining permutation relays are'unoperated. With relays l3 and I5 operated, a grounding circuit may be traced from ground at thearmature of relay l5 over a, make contact, over a break contact of relay M, a mak contact of relay l3 and break contacts of relays i2 and H through the right-hand winding of storing relay 33 over conducter 49 to battery through the winding of relay 25. Relay 33 is prevented from operating in this circuit by the ground from rings 55 and 56 placed on the conductor ill.

The recorder circuit is, therefore, conditioned for recording of the character set up in the transmitter T.

As the distributor arm 51 rotates, the brush 58 will engage segment 5| and thereby apply ground over the ring 52, conductor 53 and through the operating circuit of the light valve 15 to battery. During the brief passage of the brush over segment 5| the shutter i! will open and admit light to the traveling film Gil. The result will be that the film '55 will receive a distinct image of the shutter which may be in the nature of a narrow strip across the film. A portion of the film 6D is shown in Fig. 4.

Immediately after the brush 58 has passed over the last segment 5| the brush 59 will leave the segment 55 and thereby remove ground from conductor 59. The holding circuit is, therefore, opened and the relays 20 and 34 are released. At the same time, the short-circuit for relay 33 is removed and relay 33 is operated by its righthand winding over the winding of relay 20 almost simultaneously with the release of the previously operated storing relay 34. Relay 33 now applies ground over its right-hand make contact to segment 5|".

Relay 25 in releasing connects battery to magnet H] of transmitter T which operates to disengage the sending contacts from the tape.

As soon as. relay 20 has released, the brush 59 again reaches the segment .55 and applies ground to conductor 40 for locking relay 33 to its lefthand winding and armature and for reoperating relay 20,

The reapplication of ground to conductor 40 may be timed so that there will be sufficient time for the complete operation of transmitter magnet ID but also so that the selected storing relay will be locked before the opening of contacts in transmitter T causes the release of permutation relays I to IE; thus the operating circuit for the selected storing relay may be maintained over the contacts of the permutation relays until the'locking circuit is provided from the distributor.

It may be observed that relay 2|] is conditioned so that it will not operate through any right-hand winding of the storing relays to ground at the permutation relays. The transmitter T being comparatively slow in operation, it may be desirable to introduce a slow-acting relay 2! for temporarily maintaining battery on the operating circuit for the magnet Hi to insure its complete operation, even though relay 25 is quickly reoperated.

Upon operation of relay 2i] and release of relay 2| magnet I0 is released for advancing the tape and resetting of the contacts under control of a new row of perforations. In consequence, a new setting is impressed on the permutation relays which then prepare the selecting circuit for a storing relay which in this case may be assumed to be relay 33 which already has been selected. In the meantime, brush arm 51 has been traveling over segments 5| and in reaching segment 5|" ground is applied to the light valve 13 for a new recording on the film 50. When the brush arm passes over the last segment 5| ground is again removed from conductor 45 for release of relay 2|]. In'this case, relay 33 will not be released but stays locked over its two windings in series and over the ground at the permutation relays. Shortly thereafter, the locking ground will again be applied to conductor 45 thereby locking relay 33 over its left-hand winding only and reoperating relay 25. The transmitter E5 is, therefore, again operated for advancing the tape and resetting of its contacts and for resetting of the permutation relays, which operations all take place while the brush 58 tests the contacts 5| for ground applied by the preceding setting.

It will be seen that the segments 5| in the distributor are distributed over their who1e'circumference of the distributor except for a short distance which may be the width of five or six segments. While the brush arm 51 travels through one revolution the film is traveling through a unit distance 64, as indicated in Fig. 4. The location on the film of this distance may be chosen arbitrarily but for convenience may be considered as beginning when the brush 58 reaches the first segment 5|. The portion 65 on the film of each unit distance corresponds to the time of travel of the brush 58 over the thirtytwo segments 5| and the portion 65 corresponds to the open space from which segments 5| have been omitted and which is used for control functions. The light strip across the film will be placed at a predetermined distance from the starting time 69 for each unit space, as determined by the position of the selected segment 5| on the distributor. Thus, in response to the op-- eration of storing relay 34, a mark 51 will be placed across the film a certain distance from the starting time 69. During the next cycle, a mark 68 will be placed across the film due to the operation of relay 33 which will be slightly closer to the starting time 69, etc.

Upon completion of a message or upon exposure of any desired length of film, the film 6|! is removed and developed.

In the case that magnetic recording should be preferred, the circuit from the distributor ring 52 would be extended to a recording magnet for reception of the impulse and the recording magnet would make brief magnetic impressions on a traveling narrow magnetic tape or wire, as is well known in the art.

The film 60 is now inserted in :the high speed transmitting system.

This system is shown in Fig. 2 and includes a projector P and a radio transmission system I00.

The projector P includes a light source 8| and mechanism for passing the film 60 at high uniform speed through the projector, including a sprocket wheel 84 driven by a motor 85. A beam of light from the source 8| is focussed by a lens system 82 upon the film to illuminate a narrow strip across the film. As the film travels, the light will momentarily pass through the narrow transparent portions representing the characters and be focussed by a lens system 83 upon a photoelectric device 80. These elements are mounted in a light-proof enclosure 88.

The electrodes of the photoelectric cell '80 are connected in the input circuit of the radio transmitting system I which may be designed in any suitable manner and would usually include an amplifier IN, a modulator I02 and a carrier frequency amplifier I03 connected to an antenna circuit H0. The carrier frequency for the system may be derived from an oscillator circuit I05 which also is connected through a filter I06, a subharmonic generator I01 and an amplifier I08 to supply a subharmonic frequency over the switch 86 to the motor 85 for driving of the film at a uniform linear speed having a predetermined ratio to the output frequency from antenna H0.

The radio signals will be received at the receiving station (Fig. 3) by the receiving system 200 and impressed upon the cathode ray tube 300 for recording.

The incoming signals will be intercepted by the antenna 2 I 0 and will pass through a radio receiving circuit 2! I and a detector circuit 2I2. From the detector the signals are passed through a suitable amplifier equipment ,2I3 to the circuit 2M for control of the printing. A portion of the signal current is passed through the amplifier equipment 230 to the condenser Z'3I for controlof the character spacing in the printer. The branch circuit 2I6 connected immediately behind the detector 2I2 leads through a filter 22I, a, bharmonic generator 222 and an amplifier 223 over switch .224 to the rotary sweepcircuit 225 of the cathode ray tube 300.

The cathode ray tube 300 is of thegeneral type disclosed in United States Patents 2,214,019 of September 10, 1 40, 2,254,036 of August 26, 1941, 2,257,795, of October '7, 1941, 2,260,313 of October 28, 1941, all issued to F. Gray.

In the present embodiment, the tube includes the electron gun 3I0, the sweep system '320, the signal electrodes 330, the character stencil plate 340, the beam centering electrodes 350, the character spacing electrodes 360 and the fluorescent reading screen 310.

The electron gun 3I0 includes a heated cathode 3I I, a beam-shaping and accelerating electrode 3I2 and a circular focussing magnet 3I3. Suitable potentials are placed on these electrodes in accordance with knownpractice. By this means the beam may be given a well defined circular cross-section and may be shot with high speed toward the center of the fluorescent screen 370.

The rotary sweep system 320 may be arranged in any desired manner to deflect the beam and cause it to travel in a conical path, with a fixed .vertex angle and to produce an invisible circular spot on the plate 340 which normally travels in a circle concentric with the center of the plate. As shown in the drawing the sweep system includes two sets of plates 32I and. 322 arranged to provide two oscillating electrostatic fields at right angles to each other, through which the beam passes; the two fields oscillate at -degree phase angles with each other and combine to pro.- duce the desired sweep of the beam. The potentials applied to the plates SH and 322 and their phase relation are established in any well-known manner by the sweep circuit 225. For various types of such sweep circuits reference may be had to British Patent 212,305, complete accepted March 6, 1924. It is understood, however, that the frequency of the sweep circuit should be such that the beam is caused to travel through a com plete cycle once for each signal period of the incoming signals. Other types of sweep circuit may be used, for example that shown in Gray Patent 2,254,036 cited above.

The character stencil plate 340 has a plurality of stencil cuts 343 representing the various symbols or characters used in the operation and arranged in a circle near the periphery of the plate. The angular spacing between adjacent character cuts 343 is equal to the spacing between segments 5! in the distributor D and characters are omitted from a portion of the circle corresponding to the open space in the distributor where segments 5i are omitted. There will thus be one stencil cut for each segment 5|. The plate 340 is of an material that will be opaque to the electron beam and thus may be of metal; in the preferred embodiment it is of insulating material.

Cooperating with this plate are the signal electrodes 330 comprising a central rod MI and an annular electrode 332. These electrodes are connected over the circuit 2 I 4 to receive static potentials due to the amplified incoming signals, thereby setting up a radial static field directed transversely of the circular path of the electron beam. The static field is produced during a short interval corresponding to the width of the segments 5I in distributor D and acts to deflect the beam radially through an angle dependent upon the strength of the amplified signal impulse. Therefore, the beam sweeps continuously over its circular path, striking the plate 340 along a circle just inside the row of stencil cuts 343, and may at any time be deflected by the establishment of the radial field to strike a particular stencil cut corresponding to a particular segment 5I in the distributor, returning to its circular path immediately after the impulse has ceased. The beam will thus be instantaneously projected past the plate 349 through the stencil cut and will have its cross-sectional area shaped or outlined by the shadow of the stencil out. It should be understood that an adjustable biasing potential may be continuously applied to the signal electrodes for accurate control of the normal sweep circle on the stencil plate 340 and that this biasing potential may be momentarily added to or detracted from by a voltage controlled by the signals for the selection of stencil cuts.

Fig. 6 shows a portion of the stencil plate 340 more in detail. The letters 343 out in the stencil plate are kept in upright position in order that they may be printed in that position; they therefore take different angular positions in the plate relative to the path of the beam, which is shown as a shaded area 34L For this reason the beam is preferably given a circular cross-section, as shown at 34G, in order that the letters may be completely covered by the beam in any of their angular positions. In the figure the beam is shown deflected to strike the letter K. The path of the center of the beam-is indicated'by t e dottedline 84.1". The: beam may be. made, to travel in a curved path, during; the deflection, as shown at 342, so that it will completely cover the letter during its outward and inward stroke. The particular path during deflection may, of course, be shaped as desired by shaping of the amplified impulses from the receiving circuit in order that any desired effect uponthe fluorescent screen may be obtained for proper recording of the characters.

The target plate 340 carries a number of auxiliary targets in the nature of metallic segments or deposits, such as a target 344 about the letter I, which is used for lining up the system at starting, and triangular targets 345 and 346 for maintaining synchronism during operation, as will be described hereinafter. These plates may be in the nature of deposits on the insulating materialof the plate 340 and are connected by suitable conductors arranged on the back side of plate 340 and leadin through a starting circuit 240 and a synchronizing circuit 250 to the rotary sweep cir cuit 225.

The concentric electrodes 35! and 352 com-- prising the character centering electrodes 350 are connected to a suitable source of potential to establish a steady radial electrostatic field. When ever the beam is deflected by the electrode 330 to pass through a character stencil in disc 3 30 the shaped beam in passing between the electrodes 35! and 352 will be deflected to the center point 31! on the fluorescent screen 310 no matter at what point of the circular path the beam selects. a letter. The letters may thus be read in succession at the point 3H onthe screen and may be observed by a suitable optical arrangement 388. (Fig. 3A) for printing on a photosensitive surface; 39 in a continuous line. In this case the record! ing tape can should be moved at uniform speed, in a direction at right angles to the upright direction of the letters appearing on the screen 310.

However, for the purpose of printing the message in page form, a pair. of letter spacin electrodes 360 is arranged to establish a substantially uniform linear static field at a point between the electrode 350 and the screen 310. The plates 360 should be far enough apart to establish a uniform field at any particular voltage applied to the plates, so that the beam at any point of its circular sweep between the plates will be deflected in a direction parallel with a line between the plates through a given angle determined by that voltage. For this purpose the plates may be mounted either inside or outside the tube 300.

The object of this arrangement is to shift the illuminated spot 3' produced by the beam on the screen 3'!!! along, a straight recording line across the center of the screen in response to a varying voltage on the plates 360.

For a further explanation of this arrangement and its effect, reference will be m de to Fig. which is a cross-sectional view of the tube 39.6

taken along line 5+5 of Fi 3. looking toward. the fluorescent screen 316 and the recording tape' 39!. Inv this figure the circular shaded space 361 indicates the area in which. the beam will appear between the plates 366, where it will When the. Static. field is Zero, a character appearing in the space' be subjected to the static field.

36! will continue on until it reaches the center spot 3' on the screen from any part .of the area.

3.5!, With a certain static field established by it. will, be deflected toward. the ri ht, so thatany character instead-of striking at the point 31! may be caused to strike at a corresponding point along the linear recording area 362 on the screen on either side of the spot 3'. The greater the voltage applied to the plate, the further the character will be deflected from the spot 37! within the area 352. Thus, by controlling the voltage applied to the plates 369 any one character can be focussed upon any one point along the area 362, thereby enabling the spots of successive characters to strike at successive points with a desired spacing along the area 362 on the screen as the voltage is varied.

The composition of the fluorescent material of the screen 310 may be selected, as is well known in the art, to provide a sufficiently low threshold for the fluorescent effect to appear during the very brief energization by the beam with suificient intensity for recording and also to limit the duration of the luminous effect, so that undue blurring of the image on the continuously traveling record surface at 390 will be avoided. For page printing, the record surface 39l will move at a comparatively slow speed so that the luminous effect for each character may have an appreciable duration. The persistence of the images may thus be equal to the time of more than one signal cycle and be equal to as many as siX or eight cycles dependent upon the number of characters in the recording line.

The objective 380 is placed at a suflicient distance to view the entire line 362 on the fluores-- cent screen and proect it upon the surface 39!.

The photosensitive surface 39! may be a film for negative printing or a paper for positive printing in the form of a strip of sufiicient width to receive a succession of characters in a line across the strip. The strip 39l is moved longitudinally at uniform speed by any suitable means well known in the art. The surface speed is such that during the printing of a line across the strip the strip will have moved the distance between two successive lines. In order to have the lines appear at right angles to the edge of the strip the equipment 390 may be turned at a slight angle from a lin perpendicular to the linear area 3E2 n the screen to offset the effect of the constantly' moving strip on the line-up of the characters across the strip.

The operation of the receiving system will now be described.

When the system is started up the carrier will be incoming to the receiving circuit Zilll and the'su bharmonic frequency thereof will be im-' pressed upon the sweep circuit 50 that the beamv will rotate at high speed in unison with the frequency of the sending cycle established for the film 6d at the sending station which, as already stated, also is based on the carrier frequency. In the case where an extensive power system is availabl for supplying a common frequency or harmonic frequencies with sufficient accuracy at the sendingand there'c'eiving stations, it is possible to derive power from such power system for driving the film 60 at the sending station and for controlling the sweep circuit at the, receiving station- This alternative arrangementv is shown in the drawingas being applicable to the system by throwing the switches and 224 into their alternate positions. In such case the'frequenoy of the carrier would be entirely independent of the signaling frequency.

With the beam properly shaped and focussed' and the sweep properly adjusted, the beam spot 34! (Fig, 6) will travel in synchronism with the,

incoming signals and in a circle immediately inside the character stencils in plate 343. For the purpose of lining-up, the film 60 may have recorded thereon impulse spots or strips, corresponding to a certain character, repeated for a long enough time to permit adjustment of the phase of the beam relative to the incoming character. In the present system the character I is selected for this purpose. While the beam is out of phase, it will display different characters on the screen each time an impulse arrives. The phase of the beam may be varied by manual adjustment of the starting circuit 240 (Fig. 3) in any desired manner, well known in the art, and the phasing may be observed by the operator until the letter I appears on the screen. However, the correction of the phase at starting may be under conrol of the beam without the need of observation by the operator. For instance, a Variable phase shifter may be included in the two-wire or Single phase portion of the rotary sweep circuit 225 and its adjustment arranged to be controlled by handle 24| through the medium of an electromagnetically operated clutch, so that when current is passed through it the clutch becomes disengaged. The phase shifing circuit may be of the type disclosed in the U. S. Patent 1,926,877, issued on September 12, 1933, to Morrison. For the present purposes the phase shifter, as shown in Fig. 7, comprises a lattice network of two resistances 242 and 243 and two variable condensers 244 and 245 connected to the two main leads of the sweep cir cuit 225. The condensers are varied in unison by the handle 24| through the magnetic clutch 246. The clutch is energized over a contact on relay 241 to permit adjustment of the condensers for phase shifting. The winding of relay 247 is connected over the conductor 34! to the target 344 and thus will receive a current impulse every time the target 344 is struck by the beam. Thus, when the beam aproaches correct phasing, it will repeatedly strike the disc 344 placed around the stencil cut for the letter I and thereby send impulses over the start circuit 341, which will operate relay 241 to disconnect the control handle 24! for the manual adjustment from the starting circuit; the starting circuit thus will be left in the proper phasing condition.

For more accurate correction of the phasing and maintenance of synchronism the arrangement of the target plate 340, as shown in Fig. 6, includes the fast and slow segments 345 and 346 which are arranged next to each of the letter stencils, or to some of the stencils as desired,

and are connected over the fast and "slow circuits 348 and 349. respectively, to the synchronizing equipment 250 (Fig. 3) associated with the rotary sweep circuit 225. The segments 345 and 346 are arranged at opposite sides of each character stencil in the nonselective area and immediately adjacent to the correct track occupied by the beam when it is correctly deflected and in correct phase.

To consider the condition during starting after the beam has been closely enough phased to show the letter I by striking the disc 344, the beam may still strike one or the other of the targets 345 and 346 associated with the letter I. Assuming that the beam is fast, it will send impulses over the segment 345, conductor 348 and into the synchronizing circuit 254. Each impulse may establish a change in the circuit conditions of the phase controlling equipment which my be of sufficient duration to be effective when the next impulse arrives in retarding the phase of the beam. The beam may thus be gradually retarded by successive impulses representing the letter I until it no longer touches the target 345 and any tendency of the beam to advance in phase will be counteracted every time it strikes the target 345. The target 346 has a similar though opposite effect on the phasing equipment of the sweep circuit, in order to advance the phase of a slow beam until it clears the target 346. This correcting action for maintaining synchronism will, of course, be effective with any letter where the targets 345 and 346 are provided, and during normal operation.

Thus, for the starting conditions the phasing equipment may include a coarse phase adjustment in the starting circuit 240 and for maintaining synchronism the phasing equipment may include a more sensitive equipment in the synchronizing circuit 250 for fine adjustment of the phase. Whereas the coarse adjustment is made manual and is merely disconnected by the starting target 344, the fine adjustment, controlled by the fast and slow targets, may include a phase adjustment by control of the saturation of an inductance used as a phase shifter so that the impulses cause a change in inductance which advances or retards the phase of the beam, in a manner known in the art. The phase shifting equipment 250, as shown in Fig. 7, may be arranged in accordance with the principles disclosed by Morrison, in the patent referred to above, and thus comprises a lattice network of two resistances 252 and 253 and two variable inductances 254 and 255 connected to the two main leads of the sweep circuit 225. The two inductances are varied in unison either by means of the windings 258 connected over conductor 348 to the fast segments 345 or by means of the windings 259 connected over conductor 349 to the slow segments 346. For the purpose of attaining phase shift in opposite directions the cores of the two inductances are continuously magnetized by the windings 251, which thus establishes a normal inductance value for the windings 254 and 255 for the prevailing carrier frequency. When current impulses are produced in the windings 259 by the beam striking segments 345 the magnetization of the cores will momentarily be changed and the inductance of both windings 254 and 255 will be changed in unison. Current impulses through windings 258 will momentarily change the magnetization in the opposite sense and correspondingly change the inductance of windings 254 and 255 in unison. The result will be to produce corresponding phase shifts in opposite directions between the incoming carrier and the rotary sweep. At the high frequency of the sweep contemplated by the invention, the change in reactance of the inductive phase shifter 25!] will be slow enough to insure that it will persist for some time after a correcting impulse has caused the change, the time being long enough to maintain some shift of phase during a few succeeding cycles. In this manner immediately suc cessive correcting pulses from either the segments 345 or 346 may build up the correcting effect of the phase shifter 250 and thus block a persistent lack of synchronism. In order to obviate the possibility of reaction between the twophase shifting networks 240 and 250 a unilateral and 250 may, of course, also include amplifying equipments for making weak controlling impulses sufliciently effective.

At starting, the potential applied to the beam centering electrodes 350 is adjustedin the circuit 2|! (Fig. 3) until the ray is properly centered on the screen 310.

The circuit 2i 5, shown in Fig. 3, for controlling the character spacing electrodes etc will ordinarily be fixed in proper condition for providing a desired character spacing and a desired length of line. However, before the message arrives the key 238 should be closed to temporarily discharge the condenser 233 (if it has a charge) and place the potential of the suitably grounded battery 235 on one of the electrodes 368 so that they will be in condition to deflect the beam to the beginning of the printing line on the screen 31H, namely, to the spot 312 (Fig.

When the first impulse of the message arrives, it Will be amplified by amplifier 2l3 and impressed upon the character selecting electrodes 33!]. The beam will be deflected at this time for a, brief instant to pass through the particular stencil out which is placed at a phase angle within the beam sweep equal to the phase angle of the impulse within the signal cycle, and will thereafter return to the circular path for the remainder of the cycle. The deflected path for selection of the character K is indicated in Fig. 6.

While being shot through the stencil cut the beam passes into the centering field of the electrode 35!] and thereafter into the field of the character spacing electrodes 360,- where it is deflected toward the left to the beginning of the line area 362 (Fig. 5) at which point the luminous efiect produced by the beam will be observed by the camera and impressed on the traveling surface 39!. A portion of the amplified impulse current passes to the impulse storing circuit 2|5, charging the small condenser 23l for its duration. Thereafter the condenser 23! discharges comparatively slowly into the large condenser 233 which acquires a small potential opposed to that of battery 235, so that the tendency of the electrodes 360 to bend the beam toward the left will be reduced enough to cause the next character to clear the spot at which the first character appeared. The condenser circuit must therefore be designed so that the small condenser 23! will receive its charge during a small fraction of the signal cycle, and will discharge into the storing condenser 233 in the minimum available time between impulses, which will be determined by the impulse-free period of each signal cycle, as in turn controlled by distributor D (Fig. 1).

When the next impulse arrives, it is impressed on the circuit 2M to again deflect the beam, perhaps at a different point of the circuit path on disc 34!] for recording of a different character, and the beam will strike the screen 310 to make the new character visible with a proper shift relative to the preceding character. The second pulse also passes into circuit 2! 5 and recharges condenser 23!. Upon cessation of the impulse condenser 23l again discharges intocondenser 233 to further increase its voltage and to further reduce the angular deflection of the beam for the next character.

This process will continue in the manner de-- scribed causingthe condenser 233 to increase its potential to about twice the potential of battery 235 at which time the potential is sufficient to break down the gas-filled tube 234 for complete discharge of condenser 233; this will happen 14 after a character has been displayed at the right end of the line area 362, which was produced by the same impulse that causes the breakdown of the tube 234 upon its cessation.

When new the next character arrives the beam will again strike at the left end of the printing area 362 on the screen 310 and will be photographed at the beginning of a line on the surface 39!. This surface in the meantime having moved a distance corresponding to a desired line spacing, the printing will now proceed along a new recording line.

In the case of a function signal, such as space, it is of course not desirable to produce any record, for which reason there will beno stencil cut in disc 34!] corresponding to the phase angle of such a signal. Thus upon reception of such a signal the beam will be deflected from its circular path without making a record and the condenser 23! in circuit 2| 5 will be charged as for any other signal, so that the beam for the nextcharacter will be shifted two spaces along the printing line and a space will be inserted in the record.-

During the continued. operation exact synchronism with the incoming pulses will be maintained by the circuit 259 which will receive cor recting pulses from the fast and slow targets any time the beam tends to strike the letter stencils incorrectly; the stencils are out accurately to have their centers incorrect phase with the centers of the corresponding incoming pulses of the message when they arrive with the correct speed. By adjustment of the strength of the incoming voltage impulses in the circuit 2H1, the radial deflection of the beam may be increased so that it normally will strike both the fast and slow targets; in such case a differential effect by the impulses from any pair of targets may be utilized to control the synchronization, one pulse being longer than the other when the path of the beam becomes unsymmetrical with respect to the target's.

Upon completion of a message the exposed portion of the paper or film 39I is removed and developed.

It will thus be understood that the system, as described above and shown in the drawing, is capable of transmitting signals for telegraphic purposes at extremely high speeds, since the recording at the receiving end is not dependent upon mechanical operations that will affect the speed of the signals. This fact in itself will contribute materially to the secrecy of the system. Furthermore, the selectivity of the signal impulses is based on a phase relation relative to a starting instant of each cycle, which is not positively demarcated in the transmission, but is only initially established by cooperation between the two end stations. This fact in combination with the extremely high speed would make unauthorized decoding of the message difilcult.

It should be recognized that other circuit arrangements may be provided for control of the stepwise variation of the static field between the spacing electrodes without a departure from the invention. Thus, in accordance with an alternative arrangement, a control. impulse may be im-. pressed. upon the impulse storing circuit 255 by the beam once during each rotation, for which purpose a target 23 6 may be placed on the stem cil plate in the sector corresponding to the impulse free period of the signal cycle. In this case the input side of the impulse storing circuit 215: should be connected over key 239 and conductor 231 to target 236. When in this case the target'- 23B is placed in the same circle as the stencil cuts, the beam must be deflected to strike the target; for this purpose a special segment 5l' on distributor D (Fig. 1) should be permanently grounded by closing of the key 65 for recording of a second light strip across the film 6!! during each signal cycle. Thus the beam will be deflected a second time during each sweep, and this time immediately after having passed the last character stencil. The impulse produced in this manner may be used to advance the spacing of the characters along the printing line, through control of the condenser circuit 2l5, as described above. This impulse may furthermore be utilized to control the starting circuit, thus obviating the sending of letter I and obviating the starting target about the letter I. A further simplification Will be possible with this arrangement, since the synchronizing circuit may be completely controlled by fast and slow targets disposed adjacent to the target 236, in the manner already described. Since the target will be struck during each cycle the beam sweep would be corrected during each sweep and before the selection of each character. The fast and slow targets at the stencil cuts would not be required in this case.

It should be understood that for the purpose of suiting specific requirements many other details of the system may be worked out in other ways than those disclosed herein without departing from the spirit of the invention as expressed in the appended claims.

Thus for convenient reading of the message directly on the screen 310 or to suit any particular requirement of the recording and developing process for the recording surface 39!, the stencil cuts in character stencil plate 340 may be inverted for direct reading on the screen 370 and the potentials on character spacing electrodes 350 may be so applied that the display of characters along each recording line may be from right to left, as viewed in Fig. 5.

It is, of course, also possible to have the beam sweep in a path immediately outside the circular row of stencil cuts 343 in plate 340 and to apply the incoming impulses with a polarity such as to deflect the beam inwardly for the selection of a character.

Nor is the invention limited to a sweep pattern of circular or nearly circular form on the plate 340. Any other pattern which during each cycle covers all the phase angles used for selection will serve the purpose, the effect of the incoming impulses being merely to so modify the normal sweep as to cause the beam to strike the desired stencil cut.

This application is in part a continuation of my application Serial No. 461,115, filed on October 7, 1942, now Patent No. 2,379,884, issued JulylO, 1945. ,3

. What is claimed is:

1. A cathode ray device comprising means for.

producing a cathode ray beam, target mean for said beam having a plurality of selective areas and a nonselective area, deflecting means for selectively deflecting said beam for impingement upon different areas of said target means in re: sponse to received signals, and electrode means disposed in said nonselective area and connected to said deflecting means for changing the deflections of the beam away from said nonselective area and onto said selective areas in response to impingement upon said electrode means by the selectively deflected beam,

1 2.. A cathode ray device comprising means for producing a cathode ray beam, target means for said beam having a plurality of selective areas and a nonselective area, deflecting means for said beam arranged to selectively deflect the beam in two senses at substantially right angles to each other for impingement upon the different areas on said target means in response to received signals, and electrode means disposed in said nonselective area, and connected to said deflecting means for changing the deflections of the beam away from said nonselective area and onto said selective areas in response to impingement upon said electrode means by the selectively deflected beam.

3. A cathode ray device comprising means for producing a cathode ray beam, target means for said beam, deflecting means for selectively deflecting said beam to cause it to impinge upon different areas of said target means, and electrode means connected to said deflecting means for correcting the deflection of said beam in response to impingement on said electrode means by the beam for substantially accurate alignment of the beam with an area of said target means selected by said deflecting means.

4. A cathode ray tube adapted to normally produce a beam with a circular sweep of constant frequency under control by a sweep circuit which comprises a plurality of diiferentiated operating means arranged in a plane transverse of said beam and in a circle concentric with said beam sweep and a pair of concentric electrodes responsive to incoming signals of constant frequency for selectively and momentarily deflecting the beam from its normal sweep to strike any one of said differentiated means, said tube further comprising a correcting electrode disposed to be abnormally struck by said deflected beam for correcting the phase of the sweep.

5. A high speed signal receiving system for receiving signals of differently phased impulses and of constant frequency, said system comprising a cathode ray tube adapted to normally produce a beam with a circular sweep in synchronism with the signal frequency, said tube including a pair of concentric electrodes responsive to said differently phased impulses to momentarily deflect the beam from its normal sweep at corresponding phase angles of the beam sweep for selective operation, and a pair of correcting electrodes disposed immediately beyond the normal path of the beam during a deflection and connected for slightly advancing or retarding the sweep when struck by the beam during a deflection.

6. A high speed signal receiving system for receiving signals of differently phased impulses and of constant frequency, said system comprising a cathode ray tube adapted to normally producea beam with a circular sweep synchronizedwith the signal cycle, said tube including a plurality of symbol producing elements arranged in a plane transverse of the beam and disposed at different phase angles of the sweep along a circle concentric with the beam sweep, a pair of con-- centric electrodes coaxial With the beam sweep and responsive to said differently phased impulses for momentarily deflecting the beam from its normal sweep at corresponding phase anglesof the sweep to selectively strike corresponding symbol producing elements and produce symbols represented by the incoming impulses, and a pair of correcting electrodes disposed at each of l7 a plurality'of said symbol producing elements and immediately beyond the normal track of the beam during a deflection and connected for slightly advancing or retarding the beam sweep when abnormally struck by'the beam during a deflection.

7. A translating system comprising a cathode ray device including means for producing an electron beam, a target for said beam having a plurality of differentiated areas, deflecting electrode means for deflecting said beam to impinge selectively upon said areas, and correcting electrode means arranged adjacent said target areas; said system further comprising circuit means connected between said correcting electrode means and said deflecting electrode means and responsive to impingement by the beam upon said correcting electrode means to correct the deflection of the beam for substantially accurate alignment of the beam with any one of said areas selected by said deflecting means.

8. A translating system comprising a cathode ray device having means for producing an electron beam, target means having a plurality of difierentiated areas disposed in succession for selective impingement thereon by the beam, deflecting means for progressively controlling the movement of the beam to selectively impinge upon said areas, and correcting electrode means disposed beyond the outlines of said areas for fortuitous impingement thereon by the beam; said system further comprising circuit means connected between said deflecting electrode means and said correcting electrode means to be responsive to the said fortuitous impingements for substantially eliminating the fortuitous impingements by correcting the deflections of the beam.

9. A high speed translating system comprising a cathode ray device having means for producing a beam with a normal sweep in synchronism with incoming signals, target means having a plurality of differentiated target areas disposed for selective impingement thereon by the beam during its sweep, selective electrode means responsive to selectively phased pulses of the signals to deflect the beam from its normal sweep into impingement upon a selected one of said areas, and correcting target areas disposed beyond said differentiated areas to be exposed to impingement by said beam; said system further comprising receiving circuit means connected to impress the incoming signals upon said selective electrode means and said beam producing means, and correcting circuit means connected to receive impingement pulses from said correcting areas and to impress them upon said beam producing means to substantially confine the beam impingements to said differentiated areas.

10. A translating system comprising a cathode ray device adapted to normally produce a beam with a circular sweep of constant frequency under control of a sweep circuit and including target means for said beam having a plurality of differentiated target areas disposed in a circle concentric with the sweep and at predeter- 18 mined phase angles, selective beam control means responsive to selectively phased pulses of incoming signals to cause said beam to impinge upon a preselected one of said areas, and a plurality of correcting target areas disposed to be abnormally impinged upon by said beam for producing correcting pulses; said system further comprising phase shifting circuit means connected to respond to said correcting pulses to change the phase of the beam sweep and thereby correct for the abnormal beam impingements.

11. A translating system comprising a cathode ray device including means for producing a beam with a normal circular sweep under control of incoming signals, target means for said beam having a plurality of differentiated target areas disposed in a circle concentric with the beam sweep and spaced at equal phase angles, and selective beam control means responsive to differently phased pulses of the signals to selectively deflect the beam from its circular sweep into impingement upon a preselective one of said difierentiated target areas, said target means also having a plurality of correcting target areas disposed adjacent to said differentiated target areas to be exposed to impingement by the beam when the selective deflection of the beam deviates excessively from the normal phase angles; said system further comprising receiving circuit means connected to impress the incoming signals upon said beam producing means and upon said beam control means, and a phase shifting network connected to receive impingement pulses from said correcting target areas and impress them upon said beam producing means to correct the phase of the sweep relatively to said differentiated target areas.

12. A system for maintaining a cylically and periodically moving beam in synchronism and phase with primary frequency setting means comprising primary frequency setting means, a discharge tube, energy supplying means for setting up a beam discharge across said tube from a cathode to anode elements, means including secondary frequency setting means for moving said beam cyclically over a plurality of said anode elements, supplemental anode means in said tube, means controlled by interaction of said beam with said supplemental anode means to act to change the phase of said beam with respect to said primary frequency setting means in a manner which is acceleratory, nil, or deceleratory, dependent upon the instantaneous relative phase of said beam and said primary frequency setting means.

HARRY A. BURGESS.

REFERENCES crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,379,880 Burgess July 10, 1945 2,275,017 McNaney Mar. 3, 1942 

